1. Field of the Invention
The present invention relates to a semiconductor circuit for a speed control of an electric motor, and more particularly to a monolithically integrated semiconductor circuit for speed control of an electric motor in which an electric voltage, depending on the actual value of the speed, is generated by means of a sensor and is employed for controlling an adjusting element which influences the speed in the sense of a feedback coupling by way of the current feeding of the electric motor.
2. Description of the Prior Art
A semiconductor circuit of the type generally set forth above is described in general in the publication "Elektronik", 23, No. 1/1974, pages 9-12, and is illustrated in the circuit diagram in this publication. In the circuit disclosed therein, a tachometer is coupled to the axis of the motor and emits a voltage which is proportional to the speed. Furthermore, a thyristor, particularly a triac is provided as an adjustment element which regulates the sinusoidal a.c. current, particularly the conventional supply a.c. current, driving the motor in the sense of a phase control, i.e. allows more or less or the half wave concerned to reach the motor. The actual regulating circuit is constructed as an analog circuit and employs capacitors and resistors in addition to transistors and diodes.